This invention relates generally to store carriers for mounting a releasable store on an aircraft and, more particularly, to a stores ejection system from which stores are released with ejective force applied at forward and aft locations by thrusters which are actuated by cold, clean pressurized gas, such as air.
The store referred to herein may be used to contain munitions, such as bombs, or contain other material to be dropped from an aircraft. Military aircraft used to dispense bombs, rockets, and other stores in flight usually include racks located beneath the wings and fuselage designed to release the stores upon command. Typical racks are shown in U.S. Pat. Nos. 4,043,525; 4,347,777; 5,583,312; 5,907,118; and 6,035,759 each by the same inventor and assignee as in the present application and incorporated herein by reference.
At the time of target acquisition, a release mechanism is activated which results in mechanical release and subsequent forcible ejection of that weapon away from the aircraft. State of the art bomb ejector racks utilize pyrotechnic cartridges that on ignition, generate high pressure gas for actuating the mechanical release mechanism, as well as for providing high pressure to ejection rams which forcibly eject the store from the aircraft. This method was originated at Douglas Aircraft Company, formerly an operating division of McDonnell Douglas Corporation, in 1944, and is currently a widely used method on all weapon release devices.
While such pyrotechnic cartridges provide a weight efficient means of storing and releasing energy as a power source, they also have certain undesirable characteristics. For example, a great deal of cleaning and maintenance is required after firing a pyrotechnic device, at the cost of a great deal of labor and downtime for the aircraft. When fired, the chemical burning of the explosive charge within the pyrotechnic cartridge results in a large amount of residue being deposited within the system. This residue also contains moisture and corrosives. After burning, the moisture in the system tends to further gather debris, form ice, and otherwise clog the internal and external workings of the bomb rack mechanism. Thus, if not properly disassembled and cleaned after a scheduled number of firings, the stores rack will quickly become corroded and unreliable, and will require replacement.
Other problems associated with the use of pyrotechnic cartridges in bomb ejector systems include the necessity for use of hazardous cleaning solvents, which pose their own unique stowage, use, handling, and disposal considerations. Additionally, ground crew post-flight action is required to remove and dispose of the spent cartridges. Removal of live cartridges is required prior to off-loading unreleased stores, further increasing crew workload and turnaround time. Furthermore, prior to cartridge installation, the ground crew must utilize special equipment to conduct stray voltage checks, in order to assure that an inadvertent firing will not occur. Logistically, adequate supplies of cartridges must be maintained to support bomb rack operation, which imposes additional unique shipping, storage, and handling requirements because of their explosive nature. Cartridges have a limited shelf life as well, before becoming unreliable, so date monitoring and inventory control is necessary. Finally, parts life of the stores rack is limited because of the effects of pyrotechnic gas erosion, resulting in significant logistic and cost burdens.
Stores ejection systems are known in the prior art which avoid the use of pyrotechnic cartridges. For example, U.S. Pat. No. 4,204,456 to Ward discloses a pneumatic bomb ejector, which uses a suitable pressurized gas, such as air or nitrogen, as a stored energy source for actuating the ejector. However, the system is disclosed as being utilizable only with a particular type of customized mechanism which does not employ ejector rams to forcibly eject the store. This means that it may only be used for applications wherein it is not necessary to ensure that the store clears the aircraft slipstream by forcibly ejecting it away from the aircraft. Furthermore, the Ward system is not adaptable to the standardized ejection systems in use in almost all existing military aircraft, limiting its practical applicability. Another problem with the Ward system is that the gas is pre-charged prior to operation. However, as the aircraft climbs to altitude, and the ambient temperature drops, the pressure level drops as well. As the pressure level varies, so does the performance output. Without an onboard pressure maintenance system, the stores ejector may not operate reliably.
Another prior art approach is disclosed in U.S. Pat. No. 4,905,568 to Hetzer et al. This patent discloses an ejector mechanism which, like that of Holt, utilizes high pressure gas, preferably nitrogen, as an energy source, with hydraulics as the energy transfer medium. Hetzer does attempt to compensate for pressure variations in the stored accumulator gas by employing heating coils to alter temperature of the gas as altitude changes. However, no central control system is disclosed to independently monitor and control the pressure of multiple accumulators.
Still another prior art approach is disclosed in U.S. Pat. No. 5,583,312 to Jakubowski, Jr. where a renewable energy source is provided to power an ejector mechansim. The renewable energy source comprises and on-board compressor that is used to pressurize one or more accumulators. As pressure varies in an accumulator, gas is released through a vent valve to reduce the pressure, and gas pressure is increased by actuating an on-board compressor. Some problems with an on-board compressor can comprise the compressor adding undesirable weight, occupying undesirable space, requiring large amounts of aircraft electrical power, requiring additional aircraft wiring, generating significant heat which must be managed, high cost and long charge times, particularly where the compressor fills multiple racks.
As can be seen, there is a need for an improved apparatus and method that monitors and maintains the pressure of gas contained in multiple accumulators for use by a stores ejection system.
In one aspect of the invention, a stores ejection system for retaining a plurality of stores on an aircraft and forcibly jettisoning the stores away from the aircraft, the ejection system may comprise a plurality of ejector mechanisms, each ejector mechanism for releasably holding and releasing a store away from the aircraft; a plurality of storage devices, each storage device for storing pressurized gas at an operating pressure selected for actuating an ejector mechanism to release a store and forcibly jettison the store; a plurality of dump valves, each dump valve movable between a closed position in which a storage device is isolated from an ejector mechanism, and an open position in which pressurized gas is free to flow from the storage device to the ejector mechanism for pneumatic actuation of the ejector mechanism to release and jettison the store; a plurality of heaters, each heater operable to heat the pressurized gas within a storage device to increase the pressure of the gas contained within to an operating pressure; and a thermal central control unit for detecting the pressure within each of the plurality of storage devices, activating a heater to heat an individual storage device that is below the operating pressure, and deactivating the heater when the individual storage device reaches the operating pressure.
In another aspect of the invention, a control system for monitoring and maintaining the pressure in accumulators used to provide energy to operate a stores ejection system on an aircraft may comprise, at least one sensor for providing data indicating the pressure within an accumulator; at least one heater adapted to heat the accumulators; and a central processing unit in communication with said sensor and said heater, for receiving said data, determining whether the pressure within an individual accumulator is below operating pressure, activating a heater until the pressure within said individual accumulator reaches a predetermined level and receiving a signal from a management unit to actuate said stores ejection system.
In another aspect of the invention, a stores ejection system, for holding a store on the underside of an aircraft and forcibly releasing the store away from the aircraft, comprises a plurality of ejector mechanisms, each ejector mechanism for releasably holding and releasing the store away from the aircraft; a plurality of storage devices, each storage device for storing pressurized gas at an operating pressure selected for actuating an ejector mechanism to release the store, each storage device being free of connection to any pressure source on board the aircraft; a plurality of dump valves, each dump valve movable between a closed position in which a storage device is isolated from an ejector mechanism, and an open position in which the pressurized gas stored within the storage device is free to flow from the storage device to an ejector mechanism for pneumatic actuation of an ejector mechanism to release the store; a fill valve for initial charging of said plurality of storage devices, the fill valve being constructed and arranged to permit filling of each storage device only while the aircraft is in a landed condition; a plurality of heaters, each heater operable to heat the pressurized gas within a storage device to increase the pressure of the gas contained within to the operating pressure; and a thermal central control unit for detecting the pressure within each of said plurality of storage devices, activating a heater to heat an individual storage device that is below said operating pressure and deactivating said heater when said individual storage device reaches the operating pressure.
A method of holding and releasing a store from an aircraft while in flight, the aircraft having a stores ejection system comprising a plurality of ejector mechanisms and a plurality of storage devices, the method comprising the steps of connecting the plurality of storage devices with a pressure source located external to the aircraft and filling the plurality of storage devices prior to take-off with a gas until the pressure within each filled storage device reaches an operating pressure selected for actuating an ejector mechanism to release a store and forcibly jettison the store away from the aircraft, monitoring the pressure of the gas contained within each of the plurality of storage devices; detecting a pressure drop in at least one of the plurality of storage devices; and heating the gas in each storage device having a pressure below operating pressure to increase the pressure of the gas contained within to the operating pressure.